The present invention relates to an electron beam exposure apparatus and method, and a device manufacturing method and, more particularly, to an electron beam exposure apparatus and method in which exposure is performed by making a source emit an electron beam to form an image by the electron beam, and reducing and projecting the image on a target exposure surface by a reduction electron optical system, a stencil mask type electron beam exposure apparatus, and a device manufacturing method to which the above apparatus or method is applied.
Examples of electron beam exposure apparatuses are apparatuses of a point beam type which uses a spot-like beam, a variable rectangular beam type which uses a beam variable in its size and having a rectangular section, and a stencil mask type which uses a stencil to form a beam having a desired sectional shape.
The point beam type electron beam exposure apparatus is exclusively used for research and development purposes because of low throughput. The variable rectangular beam type electron beam exposure apparatus has a throughput higher than that of the point beam type apparatus by one to two orders, though the problem of throughput is still serious when forming an exposure pattern in which about 0.1 .mu.m fine patterns are highly integrated. The stencil mask type electron beam exposure apparatus uses a stencil mask having a portion corresponding to a variable rectangular aperture in which a plurality of repeated-pattern-through-holes are formed. The stencil mask type electron beam exposure apparatus can advantageously form repeated patterns by exposure, and its throughput is higher than that of the variable rectangular type electron beam exposure apparatus.
FIG. 2 shows the arrangement of an electron beam exposure apparatus having a stencil mask. An electron beam from an electron gun 501 is irradiated on a first aperture 502 for defining the electron beam irradiation area of the stencil mask. The illumination electron beam defined by the first aperture irradiates the stencil mask on a second aperture 504 through a projection electron lens 503 so that the electron beam passing through repeated-pattern-through-holes which are formed in the stencil mask is reduced and projected on a wafer 506 by a reduction electron optical system 505. The images of the repeated-pattern-through-holes are moved on the wafer by a deflector 507 to sequentially expose the wafer.
The stencil mask type electron beam exposure apparatus can form repeated patterns by a single exposure operation, so the exposure speed can be increased. However, although the stencil mask type electron beam exposure apparatus has a plurality of pattern through-holes, as shown in FIG. 3, the patterns must be formed in advance as the stencil mask in accordance with the exposure pattern.
Because of the space charge effect and the aberrations of the reduction electron optical system, the exposure area which can be exposed at once is limited. If a semiconductor circuit needs so many transfer patterns that they cannot be formed in one stencil mask, a plurality of stencil masks must be prepared and used one by one. Time for exchanging the mask is required, resulting in a large decrease in throughput.
When the stencil mask has patterns with different sizes, or when the pattern is a combination of patterns with different sizes, the blur of the exposure pattern caused by the space charge effect changes depending on the size of the pattern. Since the refocus amount changes depending on the size of the pattern accordingly, the blur cannot be corrected by refocusing. Therefore, such a pattern cannot be used as a stencil mask pattern.
An apparatus for solving this problem is a multi-electron beam exposure apparatus which irradiates a plurality of electron beams on the sample surface along designed coordinates, deflects the plurality of electron beams along the designed coordinates to scan the sample surface, and at the same time, independently turns on/off the plurality of electron beams in correspondence with the pattern to be drawn, thereby drawing the pattern. The multi-electron beam exposure apparatus can draw an arbitrary pattern without using any stencil mask, so the throughput can be increased.
FIG. 38A shows the arrangement of the multi-electron beam exposure apparatus. Reference numerals 501a, 501b, and 501c denote electron guns capable of independently turning on/off electron beams; 502, a reduction electron optical system for reducing and projecting the plurality of electron beams from the electron guns 501a, 501b, and 501c on a wafer 503; and 504, a deflector for deflecting the plurality of electron beams reduced and projected on the wafer 503.
The plurality of electron beams from the electron guns 501a, 501b, and 501c are deflected by the same amount by the deflector 504. With reference to the beam reference position, each electron beam sequentially sets its position on the wafer and moves in accordance with an array defined by the deflector 504. The electron beams expose different exposure areas in exposure patterns to be formed.
FIGS. 38B to 38D show a state in which the electron beams from the electron guns 501a, 501b, and 501c expose the corresponding exposure areas in exposure patterns to be formed in accordance with the same array. While setting and shifting the positions on the array in the order of (1,1), (1,2), . . . , (1,16), (2,1), (2,2), . . . , (2,16), (3,1), each electron beam is turned on at a position where an exposure pattern (P1, P2, P3) to be formed is present to expose the corresponding exposure area in the exposure pattern (P1, P2, P3) to be formed (i.e., a so-called raster scan is performed).
However, in the multi-electron beam exposure apparatus using a raster scan, when the size of the exposure pattern to be formed is small, each electron beam must be turned on at a position defined by further finely dividing the exposure region of the electron beam (the array interval of the array defined by the deflector 504 decreases). As a result, with the same exposure area, the number of times of setting the position of the electron beam and exposing the area increases, resulting in a large decrease in throughput.
FIG. 43 shows the main part of the multi-electron beam exposure apparatus. Reference numerals 501a, 501b, and 501c denote electron guns capable of independently turning on/off electron beams; 502, a reduction electron optical system for reducing and projecting the plurality of electron beams from the electron guns 501a, 501b, and 501c on a wafer 503; 504, a deflector for scanning the plurality of electron beams reduced and projected on the wafer 503; 505, a dynamic focus coil for correcting the focus position of the electron beam in accordance with any deflection errors generated in the electron beam passing through the reduction electron optical system 502 when the deflector 504 is actuated; and 506, a dynamic stigmatic coil for correcting the astigmatism of the electron beam in accordance with the deflection errors.
With the above arrangement, the plurality of electron beams are scanned on the wafer to expose the wafer in which the exposure areas of the electron beams are adjacent to each other.
However, the deflection errors generated in the plurality of electron beams passing through the reduction electron optical system 502 when the deflector 504 is actuated are different from each other. For this reason, even when the focus position and astigmatism of each electron beam are corrected by a dynamic focus coil and a dynamic stigmatic coil, optimum correction for each electron beam can hardly be performed.